I. Field
The present disclosure relates generally to communication, and more specifically to techniques for generating and using codebooks in multiple-input-multiple-output (MIMO) wireless communication system.
II. Relevant Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so forth. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems including E-UTRA, and orthogonal frequency division multiple access (OFDMA) systems.
An orthogonal frequency division multiplex (OFDM) communication system effectively partitions the overall system bandwidth into multiple subcarriers, which may also be referred to as frequency sub-channels, tones, or frequency bins. For an OFDM system, the data to be transmitted (i.e., the information bits) is first encoded with a particular coding scheme to generate coded bits, and the coded bits are further grouped into multi-bit symbols that are then mapped to modulation symbols. Each modulation symbol corresponds to a point in a signal constellation defined by a particular modulation scheme (e.g., M-PSK or M-QAM) used for data transmission. At each time interval that may be dependent on the bandwidth of each frequency subcarrier, a modulation symbol may be transmitted on each of the frequency subcarriers. Thus, OFDM may be used to combat inter-symbol interference (ISI) caused by frequency selective fading, which is characterized by different amounts of attenuation across the system bandwidth.
Generally, a wireless multiple-access communication system may concurrently support communication for multiple terminals that communicate with one or more base stations via transmissions on downlink and uplink. The downlink refers to the communication link from the base stations to the terminals, and the uplink refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out (SISO), multiple-in-single-out (MISO) or a multiple-in-multiple-out (MIMO) system.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels. Generally, each of the NS independent channels corresponds to a dimension. The MIMO system may provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. A MIMO system also supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the downlink and uplink transmissions are on the same frequency region so that the reciprocity principle allows estimation of the downlink channel from the uplink channel. This enables an access point to extract transmit beam-forming gain on the uplink when multiple antennas are available at the access point.
Development of mobile wireless broadband networks, or telecommunication networks, has been directed primarily to improving various aspects of network performance (e.g., data rates, network latency, control overhead, resource utilization . . . ) within an allocated bandwidth in order to offer subscribers a better experience and ensuing perceived quality of service when utilizing applications which demand high data throughputs. In communication systems (e.g., LTE Advanced (LTE-A) Release 10), uplink (UL) spatial multiplexing of up to four layers is supported with wide-band precoding (e.g., application of a single precoding matrix per UL component carrier). In wide-band precoding, single-carrier waveform may be maintained at each antenna in a set of antennas in a user equipment (UE) and, generally, a single precoding matrix indicator (PMI) is signaled.
Advanced telecommunication networks may include a number of base stations that may support communication for a number of UEs. A base station may include multiple transmit and/or receive antennas. Each UE may include multiple transmit and/or receive antennas. For downlink (DL) transmissions, base stations may select a precoder (e.g., precoding matrix) of a codebook used for precoding the transmitted signals. The selection of codebook by a base station may depend, in part, on feedback signals received from UEs. Some systems, such as LTE Release 8 (referred to as “Rel-8” in this disclosure) may not support codebooks for greater than four transmit or receive antennas.